#include "at91sam7s256.h" #include "crt0.h" #include "aic.h" /* The board is clocked at 48MHz */ #define CLOCK_FREQ 48000000 /* The Periodic Interval Timer runs at 3MHz. */ #define PIT_FREQ (CLOCK_FREQ/16) /* This counter keeps the system time. It is currently used only for * the sleep code. */ static volatile unsigned long tick_ms; static void sys_timer_isr() { unsigned long status; /* The PIT requires reading the status register to acknowledge the * interrupt. Let's do that. */ status = *AT91C_PITC_PIVR; /* Increment the system counter. */ tick_ms++; /* Manually trigger the low priority kernel interrupt. This low * priority interrupt will do all the slower tasks, that can be * interrupted by hardware needing fast irq handling. * * TODO: Enable this when it has something to do. */ //aic_trigger_irq(AT91C_ID_PWMC); } void sys_timer_init() { interrupts_disable(); /* Set the Periodic Interval Timer to a tiny interval, and set it * disabled. This way, it should wrap around and shut down quickly, * if it's already running. */ *AT91C_PITC_PIMR = 1; /* Wait for the timer's internal counter to return to zero. */ while (*AT91C_PITC_PIVR & AT91C_PITC_CPIV); /* Install the interrupt handler for the system timer, and tell the * AIC to handle that interrupt. */ aic_install_isr(AT91C_ID_SYS, sys_timer_isr); aic_enable(AT91C_ID_SYS); /* Configure the Periodic Interval Timer with a frequency of * 1000Hz. The timer is enabled, and will raise the interrupt we * installed previously 1000 times a second. */ *AT91C_PITC_PIMR = (((PIT_FREQ/1000)-1) | AT91C_PITC_PITEN | AT91C_PITC_PITIEN); interrupts_enable(); } unsigned long sys_timer_get_ms() { return tick_ms; } void sys_timer_wait_ms(unsigned long ms) { volatile unsigned long final = tick_ms + ms; while (tick_ms < final); } void sys_timer_wait_ns(unsigned long ns) { volatile unsigned long i = (ns >> 7) + 1; while (i) i--; }